The present invention relates to a zoom lens.
There is known a zoom lens comprising a front lens group having a positive focal length and a rear lens group having a negative focal length, the distance between the front and rear lens groups being variable for varying its magnification ratio. This zoom lens is advantageous in that since it has only two movable lens groups, the mechanism for moving the lens groups is simple, and the entire length of the zoom lens can be reduced because the magnification of the rear lens group is 1 at all times. Therefore, various zoom lenses of this type have heretofore been proposed. Most of the proposed zoom lenses have a magnification ratio of 2 or less which is the ratio between the focal length of the zoom lens at the telephoto end of the zooming movement and the focal length thereof at the wide angle end of the zoom lens stroke, and only few zoom lenses having a magnification ratio exceeding 2 are known. One of such few zoom lenses, which is disclosed in Japanese Laid-Open Patent Publication No. 62-264019, has achieved a magnification
However, the performance of the disclosed zoom lens has proven unsatisfactory because the chromatic aberration thereof caused by its magnification is not sufficiently corrected. More specifically, since the chromatic aberration of the rear lens group caused by the magnification is not sufficiently corrected, as the rear lens group is moved, the chromatic aberration of the entire zoom lens system caused by the magnification of the image plane varies. This tendency is greater as the magnification ratio becomes larger.